Process of and composition for rendering hydrophilic an image area on a lithographic printing plate

ABSTRACT

The image areas of a lithographic printing plate are rendered hydrophilic by being coated with a solution comprising a specified basic organic polymer, a cationic surfactant and an organic gelatin solvent.

United States Patent Thomas I. Abbott;

Donald A. Smith, Rochester, N.Y. 588,707

Oct. 24, 1966 Mar. 9, 1971 Eastman Kodak Company Rochester, N.Y.

[72] Inventors [21 Appl. No. [22] Filed [45] Patented [73] Assignee [54] PROCESS OF AND COMPOSITION FOR RENDERING HYDROPl-IILIC AN IMAGE AREA ON A LITHOGRAPHIC PRINTING PLATE [50] Field ofSearch 101/451,

[56] References Cited UNITED STATES PATENTS 3,161,518 12/1964 Deal et al 96/33x 3,276,361 10/1966 Abbott et a1... 96/33x 3,338,164 8/1967 Webers l0l/462x 3,394,653 7/1968 Riesberg 10l/462x 3,399,994 9/1968 Wilkinson 96/33x 3,455,003 7/1969 Wood 101/148x Primary Examiner-David Klein Attorneys-WHJ. Kline, B. D. Wiese and H. E. Byers ABSTRACT: The image areas of a lithographic printing plate 4 PROCESS OF AND COMPOSITION FOR RENDERING IIYDROPIIILIC AN IMAGE AREA ON A LITHOGRAPI-IIC PRINTING PLATE This invention concerns a deletion fluid and a process of using the deletion fluid to delete printing areas from a lithographic plate comprising an oleophilic oxidized image area in hardened colloid.

In one method of preparing lithographic printing plates photographically, as described in Yackel and Abbott, US. Pat. No. 3,146,104, issued Aug. 25, 1964, a developable silver halide image is formed by means of exposure to a line or halftone subject in a hardened hydrophilic organic colloid-silver halide emulsion such as a gelatino-silver halide emulsion.

Development is carried out using a polyhydroxybenzene silver halide developer, which is either present in the emulsion or a layer effectively adjacent thereto. When the developer is oxidized in the development reaction in the presence of the hydrophilic organic colloid vehicle present in the silver halide emulsion layer, an oleophilic image is formed. ,Upon inking the moistened plate with a greasy ink and printing in a lithographic printing press the desired lithographic reproduction, which is negative to the original subject is obtained.

if, however, a positive working plate is desired, the photographic element described above may contain, in addition, a fogged silver halide emulsion as the uppermost layer. When this photographic element is exposed to a subject, and its contiguous silver halide developing agent activated, the developing agent reacts with the sensitive lower silver halide emulsion layer to form the negative image, and the unused silver halide developing agent present in the unexposed areas of the sensitive lower silver halide emulsion layer then migrates upward to the fogged silver halide emulsion layer, and when oxidized in the presence of a hydrophilic organic colloid present in this layer, forms an oleophilic image in the surface which is positive in respect to the original subject.

Occasionally it is desirable to delete part of the image on the lithographic plate prepared as above without affecting the remaining areas. Moreover, it has been desirable to delete areas from a plate which has completed a partial run so that the plate with the modified image can then be used to make additional copies with the undeleted areas unaffected.

Many agents have been applied to lithographic plates prepared as above in an attempt to delete the image. Among these have been metal salts, gums, latexes, gelatin, dichromate bleaches and silica. None of these treatments permanently removes the image without producing other effects such as press contamination, etc. Mechanical means, such as rubbing the undesired image area with fine steel wool, have also been unsatisfactory.

One of the temporary deletion systems operates by the precipitation of a hydrophilic pigment in the area to be deleted so that the hydrophobic character of the image is overcome. Such precipitates being loosely bound in the gelatin structure are soon extracted and the hydrophobic image prevails. If a replenishment is carried out through the fountain solution so that new precipitate is continually being formed, then permanent deletion can be accomplished. Such systems require special fountain solution preparations which often are not compatible with other lithographic plates.

We have found that a solution containing a basic polymer can be used to delete the image on a processed photographic lithographic plate. Advantageously, the solution contains 21 ca tionic or amphoteric surfactant and an organic gelatin solvent, Le. a material capable of swelling, dissolving or softening gelatin.

One object of this invention is to provide a deletion solution for use in deleting the image from a photographic lithographic plate comprising a tanned image area in hardened colloid. An additional object is to provide a process for deleting the image from a photographic lithographic plate comprising a tanned image area in hardened colloid. Another object is to provide a method of deleting an image from a hardened gelatin colloid layer containing therein oleophilic areas by means of a basic polymer in combination with a cationic surfactant and a gelatin solvent. A further object is to provide a deletion method which can be used with conventional fountain solutions and which does not build up on the press. A still further object is to provide a deletion method which provides short life deletion and which permits the plate to be used subsequently with the deleted areas becoming oleophilic.

The above objects are obtained by treating the surface of the plate with a solution of a basic polymer, for example, polyethyleneimine, a cationic or amphoteric surfactant, for example, cetyl trimethyl ammonium bromide and a gelatin solvent, for example, formamide. A particularly useful range of basic polymer is from 10 to 40 percent of the deletion solution, 5 to 15 percent of the cationic surfactant and 50 to percent gelatin solvent. It will be appreciated that the proportions can be varied beyond the above ranges depending upon the particular components used. The area to be deleted is coated with a solution of the three components whereby the coated area becomes hydrophilic and remains hydrophilic for a sufficient length of time to run up to 200 copies, and in many instances more.

The period of deletion can be governed by choice of the components and, of course, can be repeated after a given number of copies have been run off to provide for a longer period of deletion. It will also be appreciated that the printing ink is preferably rubbed or swabbed from the area to be deleted to facilitate coating the gelatin area with the deletion fluid.

A large number of basic polymers which are useful in our invention may be used including, for example, polyethyleneimine, polydimethyl aminoethyl methacrylate, polyvinyl pyridine, polyvinylamine, etc. Particularly useful basic polymers are the polymines having a monomeric unit structural formula of:

we C. C N \l. l.

wherein R through R are each selected from the class consisting of hydrogen and lower alkyl groups, R is selected from the class consisting of hydrogen, lower alkyl groups, hydroxy substituted lower alkyl groups, lower alkyl alkoxy groups and fatty acid residue from the reaction of a fatty acid with the imine. Molecular weights may range from about 500 to about 500,000. Particularly useful ranges may be 1000 to 100,000.

It will also be appreciated that if desired, mixtures of basic polymers, of various cationic surfactants or of gelatin solvent can be used. However, the proportions given above apply to the total amount of the basic polymer, cationic surfactant and gelatin solvent.

The deletion fluid may be applied by swab, brush, quill, sponge or by other means which will delineate the area to be deleted. If prepared in a viscous form, it may be squeezed from a compressible tube. Although it is preferable that the deletion fluid be applied to the moist plate, it can also be applied to a plate which is in a dried-down condition.

The particular gelatin solvents which are used are a matter of choice but include well-known solvents, softeners or swelling agents, such as formamide, dimethyl formamide, urea, acetamide, hexamethyl phosphoric triamide, dimethyl sulfoxide, tetrahydrothiophene-l, l-dioxide, etc.

Cationic or amphoteric surfactants may include those known in the art and include such compounds as cetyl trimethyl ammonium bromide, acyl amidoammonium sulfonic acid betaine, etc.

A particularly useful amphoteric dispersing agent has the formula:

Run. [(CH. .C 1..

wherein R is an unsubstituted alkyl group of 12 to 18 carbon atoms, m and n are numbers of l and 2, m being preferably 2, p is a number of 2 minus m and M is a cation taken from the group consisting of sodium, potassium, ammonium and hydrogen.

Included among the cationic surfactants are, for example, alkyl, aryl and aralkyl, substituted ammonium compounds and quaternary salts of heterocyclic nitrogen compounds. Specific examples include dodecyl pyridinium sulfates, cetyl pyridinium bromide, diethylaminoethyl long chain alkyl amide esters, etc.

In one embodiment, the solution contains an amount of water equivalent to the amount of polyethyleneimine, since the polyethyleneimine is supplied in the form of a 50 percent aqueous solution. Water alone, or organic solvents alone, may be used when a solvent is needed, but in many instances, better results are obtained when a miscible organic volatile solvent is also used in the solution with water. Particularly useful organic solvents are lower alcohols such as methyl alcohol. The amount of water and/or volatile solvent is a matter of choice and depends upon the desired concentration of the deleting components. It will also depend upon the method of application, for example, by brush or by viscous mixture.

The following examples are intended to illustrate the practice of our invention but not to limit it in any way.

solution and passed through the colloid mill five times. g. percent saponin solution. 1 g. l0percent formaldehyde solution. Water. cc. Water.

The emulsion was coated at 6.5 grams per square foot on a film base and dried.

The film was exposed to a line negative, then activated for 20 seconds in a 4-percent solution of sodium carbonate 1O monohydrate. The development was stopped in an acidic stop bath by a 20-second immersion.

The plate was run on a standard lithographic press using conventional inks and acid fountain solution. After 10 copies, the ink was run off and the solutions given in the following table applied to small image areas. The application was made with brush or swab for 10 to 15 seconds. The excess solution was removed, the plate swabbed with fountain solution and the press restarted. The number of copies showing complete deletion before reappearance of the last image is given in the last column of the table.

The deletion fluid could be reapplied at any time to any area which began to print prematurely to give continuous deletion for any desired number of copies. No deleterious blinding effeet was experienced as a result of continuous usage of these solutions, i.e. the accumulation of deletion solution components in the absorbent rolls of the press does not cause failure of the plate to ink properly.

Parts polymer 1 No. copies beiore image recurrence Parts surfactant 1 Parts solvent 150% PEL. r None 2 formamide 75 150% PEI 0. 5 Sullobetaine CA. do........... 200 l 50% PEI. i. 0.25 Triton X-l00 0 1 50% PEI 0.25 Triton 770 r 10 150% PEI". 0.25 Acetoquat CTAB 200 Nonc ..do o r v v v v 50 Do .Nonc 50 1 50% PEL. 0.25 Acetoquat C'IAB do 200 1 50% PEI do 2-dimcthylformamide. 200 0 5 Polyox SR 3 Iormamide.. 60 0.5 Polyacrylic acid 2 formamide. 60 150% PEI 2 dimethylsulloxide 125 l PEI r. 2 hexamethylphosphoramide 100 1 50% PEI 2 tctrahydrothiophenedioxide. 150 l 50% PEIv 2 acetamide plus 1 pt. H2O 200 50% PEI... ....2ureaplus2HzO 150 [50% PEI ..do 2 dimethyll'ormamide.

1 See following table:

Trade Name Chemical Name Sulfobetaine CA Triton X-100. Triton 7700"..." Acetoquat CTAB Polyox WSR 35 PEI EXAMPLE 1 A lithographic plate was prepared as follows according to Yackel et al., U.S. Pat. No. 3,146,104, describing a lithographic printing plate having a top layer of gelatin having a hardness equivalent to that of a gelatin layer containing from 2 g. to about 15 g. of dry formaldehyde per pound of gelatin and containing in the gelatin layer an oleophilic tanned gelatin image area.

A photographic emulsion was prepared by combining the following ingredients:

I. Fine grain silver chloride emulsion containing 1 mole of Ag per 4,350 cc. 435g.

ll. Paraffin dispersion prepared as follows:

80 g. molten paraffin dispersed in 400 cc. 10 percent photographic gelatin solution containing 5 cc. of 10 percent Alkanol B (propylated naphthalene sulfonate) solution. 10 g.

lll. 4-Phenyl catechol dispersion prepared as follows:

50 g. 4-phenyl catechol dissolved in 100 cc. dibutylphthalate at 70 C. dispersed in 500 cc. 10 percent photographic gelatin and 50 cc. 7 /zpercent saponin EXAMPLE 2 The lithographic plate described in example 1 is used with basic polymers including polydimethyl aminoethylmethacrylate, polyvinyl pyridine and polyvinyl amine with similar 60 results.

It will be appreciated that the support on which the lithographic plate is coated may be any of the customary supports used for lithographic plates. Moreover, the components of the sensitive elements of the lithographic plate can be varied appreciably in the known photographic silver halide emulsions such as silver chloride, silver bromide, silver iodide, silver bromochloride, silver bromoiodide and silver bromochloroiodide emulsions. Direct positive emulsions may be used such as those described in Leermaker US. Pat. No.

2,184,013, Kendall and Hill US. Pat. No. 2,541,472, Fallesen US. Pat. No. 2,497,875, etc.

8 A variety of hydrophilic organic colloid vehicles can be used for the silver halide emulsions for making the plate. Proteins such as gelatin, soy bean protein, casein, as well as synthetic organic colloids which are hydrophilic, such as polyvinyl alcohol, hydrolyzed cellulose esters, etc., may be used to the extent that they form the desired oleophilic image with the oxidized developing agent in the development reaction.

lt will be appreciated, of course, that our method of deletion may also be used on lithographic plates prepared by other methods than those described above. For example, lithographic plates made by using light-sensitive polymers, for example, diazo sensitized, electrostatically formed plates, mechanically prepared plates, etc. may be used providing ad'- hesion is obtained between the hydrophilic polymer and the areas to be deleted.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modificationscan be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

l. A process for rendering hydrophilic an oleophilic image area on a lithographic printing plate comprising a support having thereon a top hydrophilic colloid layer capable of adherence to a basic organic polymer, comprising coating the image area to be rendered hydrophilic with a solution comprising l-40 percent by weight of polyvinyl pyridine or a basic organic polymer, comprising monomeric units having a structural formula:

Tr. r.

wherein R through R are each selected from the class consisting of hydrogen and lower alkyl groups, R is selected from the class consisting of hydrogen, lower alkyl groups, hydroxy substituted lower alkyl groups, lower alkoxy groups and alkanoyl groups, said polymer having a molecular weight range from about 500 to about 500,000, 5l5 percent by weight of a cationic surfactant and 5085 percent by weight of an organic gelatin solvent.

2. A process of claim 1 in which the top layer comprises gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about grams of dry formaldehyde per pound of gelatin and contains in the gelatin layer an oleophilic tanned gelatin image area.

3. A process of claim 1 in which polyethyleneimine.

' 4. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is selected from the class consisting of formamide, dimethylformamide, urea, acetamide, hexamethylphosphorictriamide, dimethyl sulfoxide and tetrahydrothiophenel l-dixoide.

5. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is formamide.

the basic polymer is 6. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is acetamide.

7. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is dimethylformamide. 1

8. A product for rendering hydrophilic an oleophilic image area on a lithographic printing plate comprising 10-40 percent by weight of polyvinyl pyridine or at least one basic organic polymer comprising monomeric units having a structural formula:

wherein R through R, are each selected from the class consisting of hydrogen and lower alkyl groups, R, is selected from the class consisting of hydrogen, lower alkyl groups, hydroxy substituted lower alkyl groups, lower alkoxy groups and alkanoyl groups, said polymer having a molecular weight range from about 500 to about 500,000, 5-15 percent byweight of a cationic surfactant and 50-85 percent by weight of an organic gelatin solvent. g V p 9. A product of claim 8 in which the basic polymer is selected from the class consisting of polyethyleneimine, polydimethyl aminoethylmethacrylate, polyvinyl pyridine and polyvinyl amine.

10. A product of claim 8 in which the basiepolymer is polyethyleneimine and the gelatin solvent is selected from the class consisting of fonnamide, dimethylforrnamide, urea, acetamide, hexamethylphosphoric triamide, dimethyl sulfoxide and tetrahydrothiophene-l,l-dioxide. U H

11. A product of claim 8 in which the basic polymer is polyethyleneimine.

12. A product of claim 8 in which the basic polymer is polydimethyl aminoethylmethacrylate.

13. A product of claim 8 in which the polyvinyl pyridine. H H

14. A product of claim 8 in which the basic polymer is basic polymer is r lyv rr i 15. A product of claim 8 in which the surfactant is cetyl trimethyl ammonium bromide. n

16. A product of claim 8 in which the surfactant is lauryl amido ammonium sulfonic acid betaine. 17. A product of claim 8 in which the basic polymer is polyethyleneimine and the gelatin solvent is formarnid 18. A product of claim 8 in which the basic polymer is polyethyleneimine and the gelatin solvent is acetamide.

19. A product of claim 8 in which the basic polymer is polyethyleneimine and the gelatin solvent is dimethylformamide. 

2. A process of claim 1 in which the top layer comprises gelatin having a hardness equivalent to that of a gelatin layer containing from 2 grams to about 15 grams of dry Formaldehyde per pound of gelatin and contains in the gelatin layer an oleophilic tanned gelatin image area.
 3. A process of claim 1 in which the basic polymer is polyethyleneimine.
 4. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is selected from the class consisting of formamide, dimethylformamide, urea, acetamide, hexamethylphosphoric triamide, dimethyl sulfoxide and tetrahydrothiophene-1, 1-dixoide.
 5. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is formamide.
 6. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is acetamide.
 7. A process of claim 1 in which the polymer is polyethyleneimine and the gelatin solvent is dimethylformamide.
 8. A product for rendering hydrophilic an oleophilic image area on a lithographic printing plate comprising 10-40 percent by weight of polyvinyl pyridine or at least one basic organic polymer comprising monomeric units having a structural formula:
 9. A product of claim 8 in which the basic polymer is selected from the class consisting of polyethyleneimine, polydimethyl aminoethylmethacrylate, polyvinyl pyridine and polyvinyl amine.
 10. A product of claim 8 in which the basic polymer is polyethyleneimine and the gelatin solvent is selected from the class consisting of formamide, dimethylformamide, urea, acetamide, hexamethylphosphoric triamide, dimethyl sulfoxide and tetrahydrothiophene-1,1-dioxide.
 11. A product of claim 8 in which the basic polymer is polyethyleneimine.
 12. A product of claim 8 in which the basic polymer is polydimethyl aminoethylmethacrylate.
 13. A product of claim 8 in which the basic polymer is polyvinyl pyridine.
 14. A product of claim 8 in which the basic polymer is polyvinyl amine.
 15. A product of claim 8 in which the surfactant is cetyl trimethyl ammonium bromide.
 16. A product of claim 8 in which the surfactant is lauryl amido ammonium sulfonic acid betaine.
 17. A product of claim 8 in which the basic polymer is polyethyleneimine and the gelatin solvent is formamide.
 18. A product of claim 8 in which the basic polymer is polyethyleneimine and the gelatin solvent is acetamide.
 19. A product of claim 8 in which the basic polymer is polyethyleneimine and the gelatin solvent is dimethylformamide. 